1. Field of the Invention
The present invention relates to a developing apparatus which is available for an electrophotographic apparatus like a laser beam printer and executes a developing process in the electrophotographic processes.
2. Description of the Related Art
As a developing method in the developing process using an electrophotographic recording apparatus, there is such a method which stores magnetic toner in the periphery of a toner/carrier roller in a hopper storing magnetic toner and magnetic carrier to blend the magnetic toner with the magnetic carrier at a position close to the toner/carrier roller.
According to any conventional developing apparatus, the toner/carrier roller and a photoconductive drum are installed in parallel with each other. The toner/carrier roller is composed of a cylindrical sleeve made of non-magnetic material and a rotatable magnet which is coaxially installed inside of the sleeve so that the sleeve and the magnet can rotate in the direction opposite from each other. The toner/carrier roller is disposed at the opening of the hopper. The hopper stores magnetic toner and magnetic carrier. Initially, carrier is stored in the vicinity of the toner/carrier roller before adhering itself to the periphery of the toner/carrier roller. Toner gradually mixes itself into carrier before being held by the toner/carrier roller.
According to the above conventional structure, the carrier is gradually moved to the upper position of the hopper by the rotation of the sleeve before eventually being dispersed all over the hopper. Once the carrier fully disperses on the hopper, the blend ratio (toner density) between the toner held on the toner/carrier roller and the carrier varies, thus eventually generating uneven density of the recorded image.
Although the magnetic carrier functions to clean the surface of the sleeve, once the carrier itself disperses, the sleeve cannot be well cleaned. This in turn causes the toner to solidify on the sleeve and eventually lowers the quality of the recorded image.